WB Madhyamik Physical science Thermal phenomenon

In this blog post, we will discuss some of the important concepts and applications of thermal phenomena in physical science. Thermal phenomenon refers to the changes and effects that occur due to heat and temperature.

• Heat is a form of energy that can be transferred from one body to another by various modes, such as conduction, convection and radiation.
• Temperature is a measure of the average kinetic energy of the molecules of a substance.

Some of the topics that we will cover are:

• Thermal expansion: This is the increase in the size or volume of a substance when it is heated. Thermal expansion occurs because the molecules of a substance move faster and farther apart when they gain heat energy. Thermal expansion has many practical applications, such as thermometers, bimetallic strips, railway tracks and bridges.
• Calorimetry: This is the study of heat transfer and measurement. Calorimetry involves the use of devices called calorimeters, which can measure the amount of heat gained or lost by a substance during a physical or chemical process. Calorimetry is based on the principle of conservation of energy, which states that energy can neither be created nor destroyed, but only transformed from one form to another.
• Specific heat capacity: This is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. Specific heat capacity depends on the nature and state of the substance. For example, water has a high specific heat capacity, which means it takes a lot of heat to change its temperature. This property makes water suitable for cooling systems and climate regulation.
• Latent heat: This is the amount of heat required to change the state of a substance without changing its temperature. Latent heat depends on the type of phase transition involved, such as melting, freezing, vaporization or condensation. For example, ice has a latent heat of fusion, which means it takes a certain amount of heat to melt it into water at 0°C. Similarly, water has a latent heat of vaporization, which means it takes a lot of heat to convert it into steam at 100°C.
• Thermodynamics: This is the branch of physics that deals with the relationship between heat and other forms of energy. Thermodynamics involves the study of various laws and concepts, such as entropy, enthalpy, free energy and equilibrium. Thermodynamics helps us understand how heat engines work, how refrigerators cool and how living organisms maintain their body temperature.

some of the basic concepts and applications of thermal expansion, such as:

• The coefficient of thermal expansion, which measures how much a material expands or contracts per unit change in temperature.
• The types of thermal expansion, include linear expansion, superficial expansion and volume expansion.
• The examples and applications of thermal expansion, range from everyday objects like thermometers and bridges to scientific instruments.

The coefficient of thermal expansion

The coefficient of thermal expansion (CTE) is a property that describes how much a material changes its size or volume when its temperature changes. It is usually expressed as a fraction or percentage per degree Celsius (°C) or Kelvin (K).

For example, if a metal rod has a CTE of 0.000012/°C, it means that for every 1°C increase in temperature, its length will increase by 0.000012 times its original length. Conversely, for every 1°C decrease in temperature, its length will decrease by the same amount.

The CTE of a material depends on its atomic structure and bonding forces. Generally, softer materials have higher CTEs than harder materials, because their atoms can move more easily when heated. For example, rubber has a CTE of about 0.0008/°C, while tungsten has a CTE of about 0.000004/°C.

The types of thermal expansion

Thermal expansion can be classified into three types:

• linear expansion,
• superficial expansion and
• volumetric expansion.

Linear expansion is the increase in the length of a one-dimensional object, such as a rod or a wire, when its temperature changes.

The formula for linear expansion is:

ΔL = αL0ΔT

where ΔL is the change in length, α is the coefficient of linear expansion, L0 is the original length and ΔT is the change in temperature.

Superficial expansion is the increase in the area of a two-dimensional object, such as a sheet or a plate when its temperature changes.

The formula for area expansion is:

ΔA = βA0ΔT

where ΔA is the change in area, β is the coefficient of area expansion, A0 is the original area and ΔT is the change in temperature.

Volume expansion is the increase in the volume of a three-dimensional object, such as a cube or a sphere when its temperature changes.

The formula for volume expansion is:

ΔV = γV0ΔT

where ΔV is the change in volume, γ is the coefficient of volume expansion, V0 is the original volume and ΔT is the change in temperature.

• The coefficients of area and volume expansion are related to the coefficient of linear expansion by the following equations:

β = 2α

γ = 3α

These equations are valid for isotropic materials, which have the same CTE in all directions. For anisotropic materials, which have different CTEs along different axes, the coefficients of area and volume expansion depend on the orientation of the object.

The examples and applications of thermal expansion

Thermal expansion has many practical implications in various fields of science and engineering. Some examples and applications are:

– Thermometers: A thermometer works by measuring the change in length or volume of a liquid (usually mercury or alcohol) inside a glass tube when its temperature changes. The liquid expands more than the glass due to its higher CTE, causing it to rise or fall along a calibrated scale.
– Bridges: A bridge expands and contracts due to changes in ambient temperature, which can cause stress and deformation on its structure. To prevent this, bridges are designed with gaps or joints that allow for some movement without compromising stability.

We hope you enjoyed this blog post and learned something new about thermal phenomena in physical science. If you have any questions or feedback, please leave them in the comments section below. Thank you for reading!